Atrial fibrillation is an irregular heartbeat that can lead to blood clots, stroke, heart failure and other heart-related complications, according to the American Heart Association; an estimated 2.7 million Americans are living with atrial fibrillation.

Study lead author Evan Thacker, Ph.D., statistician in the Department of Epidemiology, wanted to investigate whether people who had not experienced a stroke had cognitive decline, or memory and thinking problems, more quickly after being diagnosed with atrial fibrillation. Stroke has previously been found to increase cognitive decline.

“We found that age-related declines in average cognitive test scores did occur faster after diagnosis of atrial fibrillation, even after accounting for other factors that can hasten cognitive decline,” Thacker said of the findings, which are published in the June 5, 2013, online issue of Neurology®, the medical journal of the American Academy of Neurology.

“This means that people with atrial fibrillation may, on average, reach a state of significant cognitive impairment or dementia at earlier ages than people without atrial fibrillation.”

Thacker and his team tracked participants in the Cardiovascular Health Study, about 5,000 people age 65 and older, with 100-point memory and thinking tests every year for an average of seven years. About 11 percent of the people developed atrial fibrillation during the study.

People with atrial fibrillation detected at age 80 had average declines in their scores of about 10 points over the next five years, compared with average declines of about six points over five years in people without atrial fibrillation. The average rates of decline differed depending on age.

“This means that people with atrial fibrillation may, on average, reach a state of significant cognitive impairment or dementia at earlier ages than people without atrial fibrillation.”

On another 90-point brain function test, people with atrial fibrillation detected at age 80 had average declines in their scores of about seven points over the next five years, compared with average declines of about five points over five years in people without atrial fibrillation.

“We believe there are at least two possible explanations for our findings,” Thacker said. “The first is that small blood clots form in the heart and then lodge in the brain, not causing any immediate symptoms, but leading to damage over time. The other is that low output of blood to the brain from the irregular heartbeat may lead to small brain damage that builds up over time.”

Thacker now wants to study the atrial fibrillation/cognitive decline link using brain imaging technology to learn more about what is happening in the brains of people with atrial fibrillation. He wants to figure out why people with atrial fibrillation on average experience faster cognitive decline.

“If we could discover the reason, then we might be able to conceive ways to prevent or reduce cognitive decline in people with atrial fibrillation,” Thacker said.

Thacker conducted this research as a Ph.D. student in the Department of Epidemiology at the University of Washington prior to coming to UAB. The study was supported by the National Heart, Lung, and Blood Institute, the National Institute of Neurological Disorders and Stroke and the National Institute on Aging.

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